How does the sky light up like this? Earth has magnetic field lines, similar to a bar magnet, that emanates from the north and the south poles creating a layer called magnetosphere. This magnetic field shields the planet from most of the solar wind that sweeps past it. This field is strongest and thickest at mid-latitudes, near the equator and weakest at the poles. As charged particles are funneled downward along magnetic field lines, protons and electrons collide with atoms and molecules of gas in Earth’s atmosphere between 40 and 240 miles above the ground. Collisions change the internal energy states of atmospheric atoms and molecules to higher levels of energy. As they relax back to normal states, they release energy in the form of light, thus the aurora.